An articulated vehicle is a vehicle having a front frame member, a rear frame member, and an articulation joint connecting the front and rear frame members. Typically, to steer an articulated vehicle right or left, the front frame member must be rotated relative to the longitudinal axis of the rear frame member about the articulation joint.
To rotate the front frame member, these vehicles commonly include articulation cylinders mounted to the rear frame member. The articulation cylinders are operated in opposite directions. That is, when one cylinder is extended forward, the other cylinder is retracted rearward and vice versa. Typically, the articulation cylinders are hydraulically controlled by a steering system commonly known as a hand metering steering unit or HMU.
Although prior art HMUs provide adequate steering control, they have several shortcomings. Foremost, hand metering steering units can not perform certain steering performance enhancements, such as snubbing, steering jerk limit control, and electronic steering adjustment. Snubbing is defined as the softening of the end of cylinder impact. Thus, it is desirable to provide an electro-hydraulic steering system for an articulated vehicle which overcomes the shortcomings of the prior art.